Jahi, we talked about this a lot if I remember correctly

[Nrdsb4]

What is the length limit of lack of heartbeat (non-cold cases) where one can expect to come back more or less normal?

The answer to that depends on whether or not the person is receiving quality CPR. CPR accomplishes what the heart beating would accomplish, if done well.

Also, can Advance Directives (or whatever they are properly called) specify how resuscitation attempts should continue?

Of course. I’ve seen advance directives that allow for CPR but not intubation, or drugs only, etc.